Propeller



Patented Dec. 29, 1931 UNITED STATES PATENT OFFICE WILLIAM ROSEN, OF ROYAL OAK, MICHIGAN IPBOPELLER Application filed Kay 15,

plane of rotation and extending sufliciently.

from said inclined portion toassure deflection of the encountered air in the desired direction, rather than permitting such air to slip between the propeller blades, counter to the air current.

- Another object is to provide ,a propeller blade with an angular portion as abovedescribed, and to vary the magnitude of the an-- gle formed by said portion with the plane of rotation, gradually reducing said angle from the inner to the outer end of the blade to compensate for progressive increase of linear speed of travel of the blade from its inner to its outer end.

Still another object is to vary the thickness of different portions of thepropeller blade, according to strains encountered by such portions.

These and various other objects the invention attains by the construction hereinafter ing drawings, wherein:

Fig. 1 1s. a view in end elevation of the improved propeller.

Fig. 2 is a side view of the same.

Fig. 3 comprises a series of cross sections taken upon the lines A, B, C, D, E, F, G, H, and I. of Fig. 1, and showing the varying angle between the leading and trailing portions of the blade.

4 is an enlarged cro ss-section, taken on the line 44 of Fig. 1.

Inthese views, the reference character 1 designates a propeller hub, and 2 a-pair of propeller blades oppositely radially projecting from said hub, the leading and trailing edges of each blade being designated respecdescribed and illustrated in the accompany- 1980. Serial No. 452,707.

tively 3 and 4. While said blades, as illustrated,'are metallic and integrated with the hub, the invention is equally applicable to detachable blades and is not dependent upon use of any particular material.

Each blade comprises leading and trailing- -portions longitudinally coextensive with the blade and meeting at an obtuse angle, as indicated at 5. The sides of the leading portion are preferably parallel, and its leading edge 3 is preferably beveled at a suitable an le, such as forty five degrees, to decrease reslst- 'ance of the blade to rotation in air or another fluid. The trailing portion of the blade forms adjacent to the hub an angle of between forty five and thirty degrees to the plane of rotation, and this angle is gradually reduced toward the outer end of the blade, at which end it amounts preferably to only about fivev degrees. The over all width of the blade is at a maximum adjacent to the hub, and is reduced gradually from the inner to the outer end of the blade. The ratio between the width of the leading portion and trailing portion of the blade is preferably two to three, and is preferably constant throughout the len h of the blade. The thickness of the lea ing portion of the bladeis preferably less than the average thickness of the trailing portion, the latter thickness being graduall decreased from the bend 5 to the trailing e ge 4.

The chief merit of the described blade lies Y in association of its thin leading portion, substantially parallel to the plane of rotation, with the relatively angular trailing portion. The function of said leading portion is to pre-' vent slippage of air in an axial direction reverse to' that intended, when subjected to pressureby the trailing portion of the blade. In the absence of the described leading portion, a considerable part of'the air encountered. by the blade would flow pastthe rear face of the blade and its pressure reaction with such face would be reversetothat of the air encountered by the front face. In other words, the construction, as described, largely increases effective displacement of air by the blade.

Thegradual decrease in the angle formed by the-trailing portion with the plane of rota- 7 tion compensates for the progressive increase in speed of linear travel of the blade from its inner to its outer end. That is to say, the outer portion of the blade by virtue of its more rapid travel effects substantially the same displacement of air as the inner portion, although the trailing portion at the outer end has considerably less angularity than at the inner end. By virtue of this gradual variation in the angularity. there is achieved a substantially uniform displacement of air by the blade throughout its length. It will be noted that the trailing portion has its maximum thickness at its juncture with the leading portion, being gradually reduced in thickness toward the trailing edge. Also, the entire blade is preferably gradually reduced in thickness from its inner to its outer end, inasmuch as the strains arising from air resist ance are progressively reduced fronrthe inner to the outer end.

By an extensive series of experiments, it has been established by applicant that the most effective ratio between the width of the leading and the trailing portions of the blade is approximately two or three. In Fig. 4 there is illustrated by arrows the compression effect upon the air by the rotating blade, and also the tendency of the trailing portion to deflect the air parallel to the propeller axis. This View further brings out the value of the lead ing portion in resisting slippage of air compressed through rotary advance of the propeller.

\Vhile it is apparent that the illustrated embodiment of my invention is well calculated to adequately fulfill theobjects and advantages primarily stated, it is to be understood that the invention is susceptible to variation, modification and change within the spirit and scope of the subjoined claims.

What I claim is:

1. A propeller blade, comprising a leading and a trailing portion, angularly intersecting, and substantially coextensive in length with said blade, the leading portion being substantially parallel to the plane of rotation, and the angularity of the trailing portion to said plane being gradually diminished from the inner to the outer end of said blade, the trail ing portion extending rectilinearly from the leading portion to the trailing edge.

2. A propeller blade, comprising a leading portion and a trailing portion, angularly intersecting and substantially coextensive in length with said blade, the leading portion being substantially parallel to the plane of rotation, and the trailing portion extending rectilinearly from the leading portion to the trailing edge, the trailing portion being gradually curved from its inner to its outer end to efifect a gradual diminution of the angle formed by said portion with the plane of rotation. v

3. A propeller blade, comprising a leading and a trailing portion, angularly intersecting, and substantially coextensive in length with said blade, the width of the leading portion being less than that of the trailing portion, and the side faces of the leading portion being both substantially parallel to the plane of rotation, the angula-rity of the trailing portion to said plane being gradually diminished from the inner to the outer end of the blade.

4. A propeller blade comprising a leading and a trailing portion, angularly intersecting, and substantially coextensive in length with said blade, the leading portion being substantially parallel to the plane of rotation, and the angularity of the trailing portion to said plane being gradually diminished from the inner to the outer end of said blade, the widths of the leading and trailing portions maintaining a ratio of substantially two to three throughout the length of said blade.

5.' A propeller blade, comprising a. leading and trailing portion, angularly intersecting, and substantially coextensive in length with said blade, the leading portion being substantially parallel to the plane of rotation and the angularity of the trailing portion to said plane being progressively diminished from the inner to the outer end of said blade, the width of the leading portion being less than that of the trailing portion, and the over all width of the blade being gradually decreased from its inner to its outer end.

6. A propeller blade, comprising leading and trailing portions, angularly intersecting and substantially coextensive in length with the blade, the leading portion being substantially parallel to the plane of rotation, the thickness of the leading portion being gradually increased from its leading edge to its juncture with the trailing portion, and the thickness of the entire blade being gradually reduced from its inner to its outer edge.

In testimony whereof I sign this specification.

WILLIAM ROSEN. 

